1. Technical Field
The present invention relates to an automatic cutter (a cutter) that cuts recording paper or other continuous paper web disposed between a movable knife and a fixed knife by causing the movable knife to move toward the fixed knife and to slide along the fixed knife to cut the medium therebetween, and relates to a printer having the automatic cutter. More particularly, the invention relates to an automatic cutter and to a printer having the automatic cutter that can discharge the cut-off portion (the paper that was cut off) in a stable condition from the paper exit.
2. Related Art
Printers that print on recording paper such as roll paper or label paper may have an automatic cutter for cutting off the printed portion of the recording paper after printing is completed. The automatic cutter is typically located downstream from a printing position (the print head position) and prior to a paper exit along a transportation path for the recording paper between the printing position and the exit. Once separated by the automatic cutter, the cut-off portion of the recording paper is discharged from the paper exit. An automatic cutter may include a scissor cutter that cause a movable knife to pivot in a scissor action to and away from a fixed knife, or a guillotine cutter in which the movable knife moves bidirectionally in a straight line to and away from the fixed knife.
Japanese Unexamined Patent Appl. Pub. JP-A-H09-19890 discloses a scissor type automatic paper cutter that is used in printers and other devices. In the automatic cutter disclosed in JP-A-H09-19890, the fixed knife is disposed with the cutting edge facing up. And the movable knife pivots at one end in the cutting direction of the movable knife between a standby position where a gap is formed between the cutting edge of the movable knife and the cutting edge of the fixed knife, and an cutting-completed position where the cutting edge of the movable knife and the cutting edge of the fixed knife overlap throughout the entire range of the cutting direction. The recording paper is transported along a transportation path so as to be inserted to the paper cutter from the fixed knife side and is discharged from the movable knife side.
The paper exit from which the cut-off portion is discharged typically has a narrow opening so that foreign matter is not inadvertently inserted from the outside, and is generally long and narrow in the cutting direction. As shown in FIG. 7, by positioning the bottom edge 100a of the paper exit 100 slightly below the cutting edge 101a of the fixed knife 101, and positioning the top edge 100b of the paper exit 100 slightly above the cutting edge 101a of the fixed knife 101, the vertical size of the opening is reduced. This prevents the paper conveyed to the automatic cutter from hitting the top edge 100b and causing a paper jam. More specifically, the positions of the bottom edge 100a and top edge 100b of the paper exit 100 and the position of the cutting edge 101a of the fixed knife 101 are determined so that the paper conveyed toward the automatic cutter is directed to a position substantially in the middle of the gap between the bottom edge 100a and top edge 100b. 
When the movable knife 102 moves toward the cutting-completed position with this paper exit 100, a stroke of a certain length is needed for the movable knife 102 to cut the paper. And the movable knife 102 overlaps the fixed knife 101 and the cutting edge 102a of the movable knife 102 moves to a position below the cutting edge 101a of the fixed knife 101. As a result, the upstream end part 103a of the cut-off 103 is thus pushed by the movable knife 102 below the bottom edge 100a of the paper exit 100. This may result in a paper jam. As a result of the upstream end part 103a of the cut-off 103 being pushed down, the downstream end part 103b of the cut-off 103 tends to be directed upward pivoting at the bottom edge 100a with the vertical movement limited by the narrow vertical size of the paper exit 100. And the upstream side of the cut-off 103 curls in the narrow gap between the fixed knife 101 and the paper exit 100. When the movable knife 102 returns to the standby position, the energy stored in the curled portion is released and causes the cut-off 103 to spring back and possibly pop out of the paper exit 100. If the cut-off 103 pops out of the paper exit 100 and falls onto the floor, for example, there is a significant loss of user convenience.